| The dynamic wireless charging technology for electric vehicles uses the alternating magnetic field as the medium of power transmission and continuously delivers the power to the receiving coil of electric vehicles without the need of without the need of parking charge.Because the dynamic wireless charging system for electric vehicles is restricted by different selection of magnetic coupling coils,different switching control modes,and the unique fluctuation characteristics of dynamic coupling,the transmission power of the system will inevitably fluctuate with the movement of electric vehicles.Therefore,based on the dynamic wireless charging system of electric vehicles,this paper studies the dynamic coupling characteristics and the fluctuation characteristics of dynamic wireless charging transmission power.First of all,this paper uses circuit theory to complete the selection of magnetic coupling structure suitable for dynamic wireless charging system of electric vehicles,compares the compensation characteristics of four compensation topologies and normalizes the compensation capacitance to select the compensation topology suitable for the dynamic coupling model.Next,bases on the basic dynamic coupling model,the analytical expression of the transmitted power of the double-staggered dynamic coupling model is derived,and the influence factors of the fluctuation and magnitude of the transmitted power in the dynamic coupling process are investigated.And on this basis,a multi-stagger dynamic coupling model is proposed.Then,by setting up the simulation model based on the finite element simulation software,the continuous motion state of the electric vehicle is discretized,and the motion of the receiving coil is regarded as the superposition of the static state at infinite time,which is analyzed according to the instantaneous magnetic quasi-static field.This paper also defines the positive reference point and the positive direction of movement in the dynamic coupling model and determines the axial spacing between the magnetic coupling structures.Bases on the dynamic coupling characteristics of single receiving and single transmitting coil,the staggered dynamic coupling model is analyzed,the mutual inductance and transmission power variation law of the staggered dynamic coupling model is further discussed,and the received power fluctuation characteristics of the two dynamic coupling models are compared and analyzed.Finally,The experimental platform of the dynamic wireless charging system for electric vehicles is built,and the step-switching control strategy of transmitting coil and the cooperative working strategy of receiving terminal of three-coil structure proposed in this paper are applied.The multi-stagger dynamic coupling model is verified by experiments,and the experimental results are in good agreement with the simulation results.The research results show that different dynamic coupling model systems have different transmission power fluctuations.The transmitted power fluctuation based on the basic dynamic coupling model presents pulsation law.However,the transmitted power fluctuation of the multi-stagger dynamic coupling model proposed in this paper fluctuates greatly only in the driving area and the exit area,and then fluctuates less in the stable operation area.In addition,the multi-stagging dynamic coupling model can not only reduce the fluctuation of transmission power of the system,but also increase the received power of the system to meet the demand of electric vehicles in the process of dynamic wireless charging. |
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